Creatinol is closely akin to Creatine, since both molecules contain a guanidino group. It is this guanidine group that binds to the phosphate group in the formation of phosphocreatine. The major difference between Creatinol and Creatine is that the former lacks a carboxylic acid functional group and instead contains a hydroxyl functional group. Where Creatine has a tendency to undergo cyclization to form Creatinine, the Creatinol lacks the carboxylic group that is necessary for the cyclization reaction to take place. Therefore, Creatinol is unable to form the inactive Creatinine, making Creatinol readily available for phosphorylation to form an energetic species like phosphocreatine.
The formation of Creatine esters has been described (Dox A W, Yoder L. Esterification of Creatine. J. Biol. Chem. 1922, 67, 671-673). These are typically formed by reacting Creatine with an alcohol in the presence of an acid catalyst at temperatures from 35° C. to 50° C. as disclosed in U.S. Pat. No. 6,897,334.
Although Creatine esters act to protect Creatine from cyclizing into its inactive form, Creatinine, removal of the ester by esterases, present throughout the body, will again make the Creatine susceptible to inactivation by cyclization. Therefore, a need exists for a Creatine-like molecule that is not as susceptible to conversion into an inactive form and can be easily absorbed by the intestine.